| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 20°F | 41°F | 30°F | 1.2" |
| February | 24°F | 47°F | 35°F | 1.2" |
| March | 28°F | 53°F | 39°F | 1.2" |
| April | 29°F | 59°F | 43°F | 0.9" |
| May | 36°F | 68°F | 52°F | 1.0" |
| June | 42°F | 77°F | 60°F | 0.7" |
| July | 49°F | 87°F | 69°F | 0.3" |
| August | 46°F | 86°F | 66°F | 0.3" |
| September | 39°F | 79°F | 58°F | 0.2" |
| October | 32°F | 64°F | 47°F | 0.9" |
| November | 27°F | 50°F | 37°F | 1.3" |
| December | 20°F | 40°F | 29°F | 1.9" |
| Index | Merrill | Oregon | National |
| Air quality index | 29 | 32 | 42 |
| Pollution index | 3,300,250 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 261 |
| Days with moderate air quality | 98 |
| Days w/ poor A.Q. for sensitive groups | 6 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.060% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.020% |
| Mercury | 0.005% |
| City | Population | Air Quality Index | National Avg. |
| Klamath Falls, OR | 21,509 | 29 | 42.0% |
| Malin, OR | 1,057 | 29 | 42.0% |
| Newell, CA | 481 | 29 | 42.0% |
| Tulelake, CA | 839 | 29 | 42.0% |
| Altamont, OR | 18,982 | 29 | 42.0% |
| Merrill, OR | 697 | 29 | 42.0% |
| City | Population | Air Quality Index | National Avg. |
| Athol, ID | 697 | 43 | 14.0% |
| Clifton, ID | 697 | 44 | 12.0% |
| Algoma, MS | 697 | 39 | 22.0% |
| Freedom Plains, NY | 697 | 36 | 28.0% |
| East Vandergrift, PA | 697 | 38 | 24.0% |
| Merrill, OR | 697 | 29 | 42.0% |
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